Boiler for firing liquid or gaseous fuel



Aug. l2, 1969 Q QspEL-r' ET AL 3,460,519

BOILER-FOR FIRING LIQUID OR GASEOUS Filed Jam 4, 196s 4 Smets-sheet 1Aug. 12, 12969n G, QSPELT ET AL 3,460,519 i v BOILERFOR FIRING LIQUID ORGASEOUS FUEL Filed Jan. 4, 1968 4 sheets-sheet 2 l Aug. 12, 1969 G,OSPELT ET AL 3,460,59 V

BOILER FOR FIRING LIQUID OR GASEOUS FUEL Filed Jan. 4. 1968 4Sheets-Sheet 3 JIAWIA Inventors: aJ/Qr @yo/f /f/ y ffy/- Allg. 12, 1969G, OSPELT ET AL 3,460,519

BOILER F011 FIRING LIQUID OR GASEOUS FUEL Filed Jan. 4, 1968 4sheets-sheet 4 United States Patent O 3,460,519 BOILER FOR FIRING LIQUIDR GASEOUS FUEL Gustav Ospelt, Vaduz, Alfred Vogt, Schaan, and HellmutGutmann, Balzer-s, Liechtenstein, assignors to Gustav Ospelt HovalwerlkAG, Vaduz, Liechtenstein Filed Jan. 4, 1968, Ser. No. 695,683 Claimspriority, application Luxembourg, Jan. 12, 1967, 52,798; Sept. 8, 1967,54,442 Int. Cl. F22h 7/12 U.S. Cl. 122-149 12 Claims ABSTRACT 0F THEDISCLOSURE A heating boiler having a iirebox extending in thelongitudinal direction of the boiler and having a closed end and an openend `with a substantial-ly oval opening, said rebox being eccentric-allylocated in said boiler and with the outer boiler wall dening a waterjacket through which extend mutually spaced tiue gas passages havingtheir longitudinal extension in the direction of the extension ofthelongitudinal axis of the Iirebox.

The present invention relates to a boiler for tiring liquid or gaseousfuel in a substantially horizontal rebox closed at one end andsurrounded by a somewhat bell-shaped water jacket, said tirebox having aportion of its circumference surrounded by flue gas passages extendingthrough said water jacket in the longitudinal direction of said treboxwhile in front of the open irebox end there is provided an overflowchamber which establishes communication between the ue gas passages andthe lirebox and which is closed by a detachable cover carrying theburner extending into the lirebox.

IBoilers of the above mentioned type have become known in which thetirebox has the customary wellknown shape of a circular cylinder so thatthe burned or flue gases which are deviated -by 180 at the closed reboxend and flow to the open rebox end leave the rebox through a round exitopening which is formed by the open iirebox end. Subsequently, theburned or flue gases pass through a nest of boiler `tubes or tube packetarranged above the rebox in the water jacket surrounding the irebox. Thesaid nest of boiler tubes or tube packet comprises a plurality of tubesof 4round or square cross section which `are arranged adjacent and aboveeach other and extend in the direction of the axis of the trebox.

It is an object of the present invention to provide a boiler of theabove general type which will have an irnproved arrangement for theguiding of the liuc or burned gases and will have an improved heattransfer from the ilue or burned gases to the boiler water.

It is another object of the invention to provide a boiler, as set forthin the preceding paragraph which will greatly improve the economy of theboiler while resulting in a compact simplified construction of theboiler.

These and other objects and advantages of the invena tion will appearmore clearly from the following specilication, in connection with theaccompanying drawings, in which:

FIGURE 1 is a vertical central section through a boiler according to thepresent invention;

FIGURE 2 represents a cross section taken along the line lI-II of FIG.l;

FIGURE 3 shows a vertical central section through a portion of a nrodiedboiler according to the invention;

FIGURE 4 is a cross section taken along the line IV-IV of FIG. 3.

FIGURE 5 is -a vertical central section through a por- ICC tion of stillanother modification of the boiler according to the invention;

FIGURE 6 is a cross section `taken along the line VI--VI Of FIG. 5;

t FIGURE 7 diagrammatically shows a view of a tin equipped pipe;

FIGURE 8 is a cross section taken Ialong the line VIII-VIII of FIG. 7;

FIGURE 9 shows a view of -a modified flue gas passage or conduit for aboiler according to the invention;

FIGURE l0 is a section taken along the line X--X of FIG. 9; and

FIGURE 11 is a section taken along the line XL-XI of FIG. 9.

The boiler :according to the present invention is char- -acterizedprimarily in that the vl'irebox Iat its open end has an oval shape andis so eccentrically arranged with regard to the substantiallycylindrical outer wall of said -boiler that the large diameter of saidoval firebox end is located in spaced relationship to and adjacent thecentral axis of the outer wall of the boiler, whereas the small diameterof said oval iirebox end passes through said central -axis while the uepassages or conduits extend through that circumferential portion of thewater jacket which has the greater radial width.

Referring now to the drawings in detail and FIGURES 1 and 2 thereof inparticular, the boiler shown in FIG- URES 1 and 2 has a water jacket 2contined toward the outside by a cylindrical outer Wall 1. Eccentricallyarranged in said water jacket 2 yand offset thereto in downwarddirection is a rebox 3 which has a circular closed iirebox end t4 and anoval, or somewhat elliptical open iirebox end 5. The large diameter ofsaid oval or elliptical open irebox end 5 is spaced from and loc-atedbelow the central axis of the outer wall 1. The small diameter of saidoval or elliptical iirebox end 5 extends through said central axis.

Whereas with a circular open firebox end the gas flow leaving thelirebox is in its lateral portions, i.e., in the marginal portionsrelatively weak in comparison to its central portion so that the outerflue gas conduits are passed thro-ugh by the flue gases to aconsiderable less extent than the central Hue gas conduits, according tothe present invention, in view of the oval or elliptical open ireboxend, the gas iiow returning in the rebox is so shaped that it leaves theirebox with an increased volume at the narrowed portion of the oval,which means within the area of the outer ue gas conduits. Also, theouter flue gas conduits are therefore acted upon and passed through bythe burned gases more intensively so that an improved exploitation ofthe heat exchanger surfaces of said flue gas conduits is realized, andin particular in these flue gas conduits the danger of an under coolingand corrosion will be avoided. Actual tests have proved that thedilerence in temperatures at which the flue gases enter the central andouter ilue gas conduits, with an oval open irebox end is considerablylower than with a customary circular open rebox end.

That circumferential portion of the water jacket 2 which has the largerradial width, in other words, that portion of the water jacket 2 whichis located about the rebox 3 has extending therethrough ue gas conduits6.

These flue gas conduits are formed by tubes 6 of flattened andapproximately oval cross section. The tubes 6 are disposed with theirlonger cross sectional dimension perpendicular to the larger diameter ofthe oval iirebox end 5 and with their longer side faces are spacedapart. While the distance between the longer sides of each tube isconstant, the depth of each tube 6 diminishes progressively in thedirection of flow of the iiue gases as it clearly shown in FIG. 1.

The oval form of the open end of the firebox, particularly at the end 5,increases the water space available for accommodation of the flue gastubes between `the wall of the firebox and the outer wall of the waterjacket so that the outer wall of the water jacket can be a conventionaland easily fabricated cylinder of sheet metal, while ample space isnevertheless available, especially for the flattened flue gas tubes 6,the major dimension of which is at the open end of the firebox. Also atthe open end of the firebox, the wall of the combustion chamber and theouter wall of the water jacket are, in view of the oval form of theouter end of the combustion chamber, over a wide range, substantiallyequally vertically spaced so that identical flattened fiue gas tubeswith substantially equal longer cross sectional dimension can beutilized and disposed adjacent one another in the water space with theirlarger side faces facing each other.

As the depth of the adjoining flattened tubes decreases towards theclosed end of the combustion chamber, which can readily be achieved withthe flattened configuration of the tubes, there is realized on one handa progressive decrease in cross sectional area of the tubes in thedirection of fiow of the gases and therefore, a substantially constantspeed of flow of the combustion gases cooling off. This has a favorableeffect on the heat transfer, and on the other hand makes it possible tomake the closed end of the combustion chamber of increased crosssectional area. The flat and somewhat oval tubes 6 have a very largesurface area and, therefore, bring about the advantage that sufficientheat exchange of the fiue gas conduits can be achieved withcomparatively few tubes so as to reduce the manufacturing costs arisingfrom welding the tubes 6 to the boiler. The iiattened tubes 6 also havethe important advantage as compared with round or rectangular tubes thatpractically no dead or incompletely utilized core develops in the gas owso that there is no need to provide in the tubes devices creatingturbulence as, for instance, spiral inserts or the like.

At the open firebox end 5, the firebox 3 and the tubes 6 are connectedby an overflow chamber or header 7 which is closed by a cover 8 andwhich carries a burner 9 projecting into the open end 5 of the firebox.The stream of burned gases owing back in the firebox 3 toward its openend is formed by the oval form of said open end 5 into a broad gasstream which is powerful and intensive at the lateral edge zones so thatthe outermost tubes 6 at the right and left hand are traversed by theseintensive parts of the gas stream. In view of the progressivelydiminishing depths of the tubes 6, the speed of travel of the burnedgases cooling off remains substantially constant so that a substantiallyconstant heat exchange occurs throughout the length of the tubes 6.

As mentioned above, the tubes 6 can readily be fabricated from strips ofwedge-shaped cut sheet metal by bending the strips longitudinally aboutwedge-shaped formers and welding the abutting edges to produce a tube ofprogressively decreasing depth. The wider sides of the tubes 6 arestiffened by transverse, preferably inwardly projecting ribs 1t), whichadditionally aid in creating a turbulence in the flue gases.

The firebox may advantageously be so designed that its cross sectiongradually merges from its oval shape at the open firebox end into acircular shape at the closed end of the firebox while both firebox endshave substantially the same circumference.

Despite providing a large heating surface which augmented by the highheat transfer from the combustion gases on their way through the boiler,yields a high boiler performance, the boiler has a compactpressure-resistant construction so that the Walls subject to thepressure of the boiler water, can be comparatively thin.

Inasmuch as the front oval shape of the firebox gradually merges withthe rear circular shape, and since both firebox ends have substantiallythe same circumference, the firebox can be made of a simple round bottomand a rectangular mantle sheet. The cylinder formed in this way is then,at its open end, compressed into the desired oval shape.

According to one advantageous construction, the boiler has a wall at theopen end of the firebox which Wall is substantially confined to the sideof the larger diameter nearer the iiue gas tubes 6 and provides anoutlet opening from the combustion chamber to the header. The boilerincludes within the header finned tubes which preferably extend at rightangles to the larger diameter of the open end of the firebox with theirfins substantially parallel to the gas fiow, while between the wall andthe cover, a burner tube extends through the header into the Iirebox.

More specifically, with the boiler according to FIGS. 3 and 4, a wall 20is provided at the open end 5 of the firebox, which wall 20 leaves anexit opening 21 from the firebox 3 to the header 7, said opening beingconfined to the side of the larger diameter of the open end remote from'the tubes 6. In this way, the space of the header 7 is taken advantageof, and the boiler heating surface and the degree of efiiciency of theboiler is greatly increased. The flue gases which also in this instanceleave the rebox in the' form of a wide gas flow strong at the marginalareas, are forced to leave the firebox 3 at the lowermost point of theheader 7 and to iiow into the latter so as to pass therethrough on aslong a path as possible up to the tubes 6. The wall 20 carries a burnertube 22 which is open to the firebox 3 and extends through the header 7up to the cover 8. The wall 20 and the burner tube 22 form walls forconfining boiler water. Within the header 7 transverse to the largediameter of the oval firebox end there are provided vertical finnedpipes 23. These finned pipes or tubes are impinged upon by the upwardlyowing flue gases so that already in the header 7 an intensive heatexchange to the boiler water occurs before the burned gases reach thetubes 6.

In this way, optimum use is made of the header. The finned tubes 23 areso arranged that the openings of the tubes 6 leading into the header 7are not covered up. In this way, when tilting the cover 8 which ishinged to the boiler, into its open position, the tubes 6 can easily becleaned between the finned pipes 23. The firebox 3 is accessible belowthe burner tube 22 for cleaning said firebox, since no finned pipes arerequired at the bottom side of the burner tube 22.

The boiler shown in FIGS. 5 and 6 corresponds in principle to the boilerin FIGS. 3 and 4. However, in contradistinction to FIGS. 3 and 4, withthe arrangement of FIGS. 5 and 6, the header does not form a part of theboiler but represents a portion of a somewhat bell-shaped cover 30 inwhich a cavity is provided on the inner side of the cover and forms aheader 31. The cover 30 is traversed by boiler water, and also in thisinstance, the header 31 comprises vertical water filled finned tubes 32.The inside of the cover 30 is provided with a burner surrounding tube 33which is filled with boiler water and extends through the header 31 intothe open firebox end S. This open end 5 is provided with a boiler waterfilled wall 34 which leaves an exit opening 35 from the fireboX 3 to theheader 31 only on that side of the large diameter of the oval fireboxend 5 which faces away from the tubes 6. The burned gases will also inthis instance be forced to enter the header 31 is deeply as possible andwith a wide gas tiow which is strong at the marginal areas. The burnedgases flow through said header up to the tubes 6 along a path as long aspossible. Since the finned pipes 32 are arranged on the inside of thecover 30 and are adapted together with the cover 3@ which is connectedto the boiler by a hinge 36 (FIG. 6), to be tilted away from the boiler,the tubes 6 and the open rebox end 5 are completely freely accessiblefrom the front for purposes of cleaning and inspection. Consequently, alarge number of closely spaced finned tubes may be arranged on theinside of the cover 30. These finned tubes may, as shown in FIG. 6 inclosed position of the cover 30 be located in front of the openings ofthe tubes 6 and also on the bottom side of the burner tube 33. Inaddition thereto, this boiler construction brings about the greatadvantage that the cavity on the inside of the cover 30` which cavityforms the header 31 may be dimensioned as deep as desired to permit atwill the welding of only one finned pipe row or according to FIG. twolinned pipe rows or more to the cover 30 without the necessity of anywelding operations on the boiler, the boiler can be altered by simpleexchange of the cover 30, for instance by the employment of a cover withthree or more rows of finned pipes the boiler output may be considerablyincreased. With this boiler construction, it is also possible to makethe finned pipes better accessible for cleaning purposes because thewater cooled cover can without any diiculties have its outside providedwith additional cleaning openings so that access will be gained tothefinned pipes from both sides. At the lowermost and highest points, thejacket 2 andthe cover 30 communicate with each other by water pipes 37.These pipes 37 are within the area of the hinge 36 provided withflexible metallic hoses to permit pivoting of the cover 30 without thenecessity of emptying the boiler and disassembling the pipes 37.

In order to assure that the fins of the tubes 23 (FIG. 3) and 32 (FIG.5) will be intensively raked by the burned gases over their entirefinned surface, the fins are advantageously so arranged that they extendsubstantially parallel to the gas ow. Tubes with fins which extend inthe direction of the gas flow, which in conformity with FIGS. 3-6 extendtransverse to the large diameter of the oval iirebox end and thus arearranged vertically, may advantageously be designed as pipes withcorrugated strips which are partic-ularly noted for the fact that theyhave an extremely large heat exchanging surface of the tins in spite ofa relatively short overall diameter. They also have a very high heattransfer capability. Such corrugated strip tube is illustrated by Way ofexamples in FIGS. 7 and 8. More specifically two elongated corrugatedmetal strips 40 and 41 are coiled helically adjoining one another aroundthe outer surface of a cylinder tube 42. The strips 40 and 41 aremetallically connected to the outer surface of tube 4Z at their zones ofcontact to provide thermal conduction. As shown in FIG. 8, thearrangement may be such that by the application of two corrugated stripsit can easily be assured that the ribs formed by the corrugated stripsare offset relative to each other from coil to coil or winding towinding so that the corrugated strip ribs of each winding can be actedupon intensively inside and outside by the burned gases.

Instead of the tubes 6, also cylindrical tubes may be employed as iiuegas channels, if the tapering of the flue gas conduits in the directionof flow of the gases is not necessary. Advantageously, the cylindricaltubes are so designed that their wall is provided with peripheraldepressions which bring about decreases or constrictions in the crosssection.

FIG. 9 is a side view of a cylindrical tube 50 having in its wall spacedtrough or groove-shaped depressions 51. This is clearly shown in FIGS.9-11. FIG. 9 shows a view of a cylindrical pipe 50 having its wallprovided with spaced bead-shaped or groove-shaped depressions 51. FIG.l0 is a cross section through pipe 50, and FIG. 1l is a longitudinalsection through pipe 50. The depressions 51 convert the smoothcylindrical pipe into a grooved tube. The depressions which can easilybe produced in ordinary cylindrical pipes by light and noncomplicatedtools have the advantage that the burned gases are subjected toconsiderable turbulence which in turn forces them to an intensive heattransfer so that special assemblies, as for instance twisted metalstrips become superfluous which heretofore had to be provided withcustomary smooth cylindrical pipe in order to produce a gas turbulence.

If desired, each cross sectional area of a pipe may be provided with twodepressions which as shown in FIG. 10 are arranged diagrammaticallyopposite to each other. However, if desired, for instance, threedepressions distributed over the circumference of the pipe or only oneannular depression may be provided. The above mentioned grooved pipesare also useful with other boiler constructions of the type mentionedabove.

It is, of course, to be understood that the present invention is, by nomeans, limited to the particular embodiments referred to above, but alsocomprises any modifications within the scope of the appended claims.

What We claim is:

1. A heating boiler which comprises: an outer portion of approximatelycylindrical shape with the longitudinal axis thereof extending in thelongitudinal direction of said boiler, an inner portion forming atirebox and having its longitudinal extension in the direction of thelongitudinal axis of said outer portion while being arranged within andeccentrically with regard to said outer portion so as to definetherewith a larger water jacket portion and a smaller water jacketportion, said iirebox having a closed end and also having an open endwith an oval opening the large diameter of which is transverse to andspaced from the longitudinal axis of said outer portion Whereas thesmall diameter of said oval opening at least nearly intersects thelongitudinal axis of said outer portion, and a plurality of iiue gaspassage means communicating with said firebox and extending into saidlarger water jacket portion in the longitudinal direction of saidiirebox.

2. A boiler according to claim 1, in which said ilue gas passage meansare formed by flattened mutually spaced tubes of approximately ovalcross section with the longer cross sectional dimension thereofapproximately per pendicular to the large diameter of said o'val openingand with their larger side faces spaced apart, the longer crosssectional dimension of said flue gas passage means continuouslydecreasing in the direction toward the closed end of said iirebox.

3. A boiler according to claim 2, in which the larger faces of the tubesare provided with ribs extending transverse to the longitudinal axes ofsaid tubes.

4. A boiler according to claim 3, in which said ribs partially extendinto the interior of said tubes.

5. A boiler according to claim 1, in which said ue gas passage means areformed by cylindrical tubes having peripheral depressions and locallyreducing the cross section of the respective tube.

6. A boiler according to claim 1, in Which the cross section of thefirebox changes its shape gradually from that end which comprises theoval opening to a circular form at the closed end of said irebox, bothends of said irebox having approximately the same peripheral length.

7. A boiler according to claim 1, which includes: a closure wallarranged at said open end of :said rebox and closing that portion onlyof said oval opening which is 10- cated on that side of said largediameter which is adjacent said ue gas passage means, a headerinterposed between and in communication with both the other portion ofsaid opening of said iirebox and said llue gas passage means, burnertube means extending from the outside of said header through the latterinto said tirebox, and iinned pipe means adapted to receive and containboiler water while communicating with said water jacket and extendinginto said header, the iins of said nned pipe means being substantiallyparallel to the gas flow.

8. A boiler according to claim 7, in which said finned pipe means extendapproximately at a right angle with regard to the large diameter of saidoval opening.

9. A boiler according to claim 8, in which said nned pipe means areformed by tubes having ondulated strips connected to the outside of saidtubes.

10. A boiler according to claim 7, in which said closure wall and saidburner tube form a part of the water jacket.

11. A boiler according to claim 8, in which said iinned 7 8 pipe meansextend laterally of the connections of said ue References Cited gaspassage means with said header. D TES PATENTS 12. A boiler according toclaim 7, in which said header UNITE STA and said finned pipe means formpart of a cover hinged 3,171,388 3/1965 Ganz 122 149 to said boiler andadapted to be pivoted selectively in a 5 312301936 1/1966 Clefwer et al'122*`149 direction away from said boiler, and in which flexible con-313291131 7/1967 Wnght 122-'149 duit means are provided connecting saidfinned pipe means with Said Water jacket. CHARLES I. MYHRE, PrimaryExaminer

